DTPTRI (3)  Linux Man Pages
NAME
dtptri.f 
SYNOPSIS
Functions/Subroutines
subroutine dtptri (UPLO, DIAG, N, AP, INFO)
DTPTRI
Function/Subroutine Documentation
subroutine dtptri (characterUPLO, characterDIAG, integerN, double precision, dimension( * )AP, integerINFO)
DTPTRI
Purpose:

DTPTRI computes the inverse of a real upper or lower triangular matrix A stored in packed format.
Parameters:

UPLO
UPLO is CHARACTER*1 = 'U': A is upper triangular; = 'L': A is lower triangular.
DIAGDIAG is CHARACTER*1 = 'N': A is nonunit triangular; = 'U': A is unit triangular.
NN is INTEGER The order of the matrix A. N >= 0.
APAP is DOUBLE PRECISION array, dimension (N*(N+1)/2) On entry, the upper or lower triangular matrix A, stored columnwise in a linear array. The jth column of A is stored in the array AP as follows: if UPLO = 'U', AP(i + (j1)*j/2) = A(i,j) for 1<=i<=j; if UPLO = 'L', AP(i + (j1)*((2*nj)/2) = A(i,j) for j<=i<=n. See below for further details. On exit, the (triangular) inverse of the original matrix, in the same packed storage format.
INFOINFO is INTEGER = 0: successful exit < 0: if INFO = i, the ith argument had an illegal value > 0: if INFO = i, A(i,i) is exactly zero. The triangular matrix is singular and its inverse can not be computed.
Author:

Univ. of Tennessee
Univ. of California Berkeley
Univ. of Colorado Denver
NAG Ltd.
Date:
 November 2011
Further Details:

A triangular matrix A can be transferred to packed storage using one of the following program segments: UPLO = 'U': UPLO = 'L': JC = 1 JC = 1 DO 2 J = 1, N DO 2 J = 1, N DO 1 I = 1, J DO 1 I = J, N AP(JC+I1) = A(I,J) AP(JC+IJ) = A(I,J) 1 CONTINUE 1 CONTINUE JC = JC + J JC = JC + N  J + 1 2 CONTINUE 2 CONTINUE
Definition at line 118 of file dtptri.f.
Author
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